Passing an array to SQL parameter with Dapper

Question

I want to insert into a table an array of values if they don't exist, the array is small and would not exceed 10 items, so it is safe to pass in an insert.

How can I execute this code with Dapper? I tried the following but I am getting an error:

const string sqlSymbolsInsert = 
    @"INSERT INTO Country (Name)
        SELECT NewNames.Name FROM (VALUES(@Names)) AS NewNames (Name)
        WHERE NOT EXISTS (SELECT 1 FROM Country AS C WHERE C.Name = NewNames.Name);";

await using var cn = new SqlConnection(CONNECTION_STRING);
await cn.ExecuteAsync(sqlSymbolsInsert, new { Names = countries.Select(x => x.Name) });

The error is:

Core Microsoft SqlClient Data Provider: Incorrect syntax near ','.

There is a similar problem on SO, but it is for the IN clause: dapper "IN" clause not working with multiple values

Is there another way in Dapper to pass an array in my case?

Answer 1

What you are trying to do isn't possible. But instead of the array, you can just use your countries collection. It has a Name property and Dapper will run the query for each item in a suitable collection:

const string sqlSymbolsInsert = 
    @"INSERT INTO Country (Name)
        SELECT @Name WHERE NOT EXISTS 
        (
            SELECT  1
            FROM    Country 
            WHERE   Name = @Name 
        )";

await using var cn = new SqlConnection(CONNECTION_STRING);
await cn.ExecuteAsync(sqlSymbolsInsert, countries);